In the art of injection molding, a typical injection mold will contain one or more mold cores and cavities that correspond to the shape of the molded article being produced. A melt stream of moldable material is injected from an injection molding machine into the mold cavities through a hot runner system, where it is allowed to solidify for a period of time before the mold is opened and the newly molded parts are ejected.
One of the most significant factors in affecting the overall cycle time required to produce one or a plurality of molded articles is the time required to solidify or cool the newly molded articles within the mold cavity before the parts are ejected.
In injection molding applications such as the molding of polyethylene terephthalate (PET) preforms, the ability to rapidly cool the molded articles in the mold is of utmost importance since the newly molded preforms are in many instances removed from the mold by a robotic post-mold cooling device as soon as they have solidified to a point where they can be handled without being damaged.
In PET molding an assembly of components, known in the art as a mold stack, defines the mold cavity in which the preform is molded. The inside surface of the preform is defined by a mold core, whereas the outside surface of the preform is generally formed in three sections. The hemispherical, or otherwise shaped, end portion being defined by a gate insert, the elongate body portion being defined by a cavity insert, and the thread/neck portion being defined by a pair of cooperating thread splits. Rapid cooling of the outside of the preform is particularly important since it is the outside of the preform that is handled by the post-mold cooing device immediately upon ejection of the newly molded article from the mold. That being said, inadequate or inefficient cooling of the outside of the preform can result in defective molded articles, and/or have a negative impact upon the time of the overall molding cycle.
As such, a need exists in the art for cooling conduit arrangements that provides rapid and efficient cooling to the elongate body portion of the preform.